Wireless communication networks exchange data for User Equipment (UE) to provide various user data services. The UEs may be phones, computers, machines, and the like. The user data services could be media streaming, audio/video conferencing, data messaging, internet access, or some other information service. Long Term Evolution (LTE) is a popular type of wireless communication network.
LTE networks include evolved Node Bs (eNodeBs) that wirelessly communicate with the UEs. The eNodeBs communicate with each other and with an LTE core network over backhaul links. The LTE core network includes a Mobility Management Entity (MME), Serving Gateway (S-GW), and other network elements. The backhaul links comprise switches, routers, and media. The switches may use various Layer 2 protocols like Ethernet. The routers may use various Layer 3 protocols like Internet Protocol (IP). The media may use metal, glass, air, space, or some other material.
FIGS. 1-2 illustrate the operation of a prior art LTE network to perform an X2 UE handover. Initially, UE 101 is attached to source eNodeB (ENB) 111. Uplink (UL) data between UE 101 and SGW 132 traverses source eNodeB 111 and backhaul 121. Likewise, Downlink (DL) data between UE 101 and SGW 132 traverses source eNodeB 111 and backhaul 121.
Source eNode B 111 receives measurement reports from UE 101 indicating signal strength for source eNodeB 111 and neighbor eNodeBs that include target eNodeB 112. Source eNode B 111 determines when UE 101 has better signal strength from a neighbor eNodeB. In this example, target eNodeB 112 provides better signal strength at UE 101 than source eNodeB 111, so in source eNodeB 111, an X2 handover is triggered for UE 101 to target eNodeB 112.
Source eNodeB 111 transfers an X2 handover request (RQ) over backhaul 121 to target eNodeB 112. The X2 handover request indicates UE bearer context and other information. Target eNodeB 112 establishes an UL to SGW 132 and generates UE attachment data. Target eNodeB 112 transfers an X2 handover response (RP) over backhaul 121 to source eNodeB 111. The X2 handover response indicates the UE bearer context, X2 tunnel data, UE attachment data, and other information.
Source eNodeB 111 now forwards the DL data (from backhaul 121 and SGW 132) to target eNodeB 112 over the X2 tunnel through backhaul 121. Target eNodeB 112 buffers the DL data. Source eNodeB 111 also transfers a reconfiguration request to UE 101 that indicates the UE attachment data for target eNodeB 112. In addition, source eNodeB 111 transfers sequence numbers to target eNodeB 112 over backhaul 121 that indicate the handover point in the DL data flow.
Referring to FIG. 2, UE 101 attaches to target eNodeB 112 using the UE attachment data. Target eNodeB 112 transfers the buffered DL data to UE 101. The UL between UE 101 and SGW 132 still traverses target eNodeB 112 and backhaul 121. Target eNodeB 112 transfers an S1 switch request to MME 131 over backhaul 121. The S1 switch request indicates the UE bearer, target eNodeB tunnel data, and other information. MME 131 transfers a modify bearer request to SGW 132, and SGW 132 returns a modify bearer response to MME 132 (interactions with the Packet Data Network Gateway are omitted here for clarity).
S-GW 132 marks the handover point in the DL data flow to source eNodeB 111. Source eNodeB 111 stops forwarding data over the X2 tunnel at the handover marker. The DL data between SGW 132 and UE 101 now traverses backhaul 121 and target eNodeB 112. MME 131 transfers an S1 switch response to target eNodeB 111 over backhaul 121. Target eNodeB 111 transfers a UE context release (REL) to source eNodeB 111 over backhaul 121. Source eNodeB 111 clears UE 101 context and the handover is complete.
FIGS. 3-4 illustrate the operation of the prior art LTE network to perform an S1 UE handover. The S1 handover is typically used when an X2 handover is not available or fails. Initially, UL data between UE 101 and SGW 132 traverses source eNodeB 111 and backhaul 121. Likewise, Downlink (DL) data between UE 101 and SGW 132 traverses source eNodeB 111 and backhaul 121.
Source eNode B 111 receives measurement reports from UE 101 indicating signal strength for source eNodeB 111 and neighbor eNodeBs that include target eNodeB 112. Source eNode B 111 determines when UE 101 has better signal strength from a neighbor eNodeB. In this example, target eNodeB 112 provides better signal strength at UE 101 than source eNodeB 111, so in source eNodeB 111, an S1 handover is triggered for UE 101 to target eNodeB 112.
Source eNodeB 111 transfers an S1 handover request (RQ) over backhaul 121 to MME 131. The S1 handover request indicates target eNodeB 112, source eNodeB tunnel data, and other information. MME 131 transfers the S1 handover request to target eNodeB 112. Target eNodeB 112 returns an acknowledgement to MME 131. The acknowledgement indicates UE attachment data and target eNodeB tunnel data. MME 131 transfers an S1 handover command (CMD) to source eNodeB 111 over backhaul 121 that indicates the UE attachment data.
MME 131 transfer an indirect tunnel request to SGW 132, and SGW returns an indirect tunnel response. The tunnel request indicates source and target eNodeB tunnels to connect. The DL data between SGW 132 and UE 101 now traverses backhaul 121 to source eNodeB 111 and then to backhaul 121 over the indirect tunnel through SGW 132 to target eNodeB 112. Target eNodeB 112 buffers the DL data.
Referring to FIG. 4, source eNodeB 111 transfers a reconfiguration request to UE 101 that indicates the UE attachment data for target eNodeB 112. In addition, source eNodeB 111 transfers sequence numbers to target eNodeB 112 over backhaul 121 and MME 131 that indicate the handover point in the DL data flow. UE 101 attaches to target eNodeB 112 using the UE attachment data. Target eNodeB 112 transfers the buffered DL data to UE 101. The UL data between UE 101 and SGW 132 now traverses target eNodeB 112.
Target eNodeB 112 transfers an S1 switch Notice (OK) to MME 131. The S1 switch request indicates the UE bearer and other information. MME 131 transfers a modify bearer request to SGW 132 and SGW 132 returns a modify bearer response to MME 132 (interactions with the Packet Data Network Gateway are omitted here for clarity). S-GW 132 modifies the DL bearer. The DL data between SGW 132 and UE 101 now traverses target eNodeB 112. MME 131 transfers a UE context release to source eNodeB 111 over backhaul 121. Source eNodeB 111 clears UE 101 context. MME 131 transfers an indirect tunnel delete (DEL) request to SGW 132. SGW 132 deletes the indirect tunnel and the handover is complete.
The prior art LTE network uses backhaul 121. Unfortunately, backhaul 121 does not intelligently assist the eNodeBs with load balancing. Backhaul 121 does not intelligently assist eNodeBs with handover operations.